:1) dmesg | less shows that DF thinks I don't have an ATA-66 cable or
: something of the like on my first IDE interface where my (only) hard

> : drive is connected, I do have an ATA-133 rated cable, and the hard
> : drive is an ATA-100 device.
>

One thing to note here... there's a good chance that you don't
actually have an ATA-133 rated cable. There are a ton of cables
being sold that look like they ought to be ATA-133 (e.g. they have
the double density wires), but in fact are not. I had a similar
scratch-the-head situation and replacing the cable fixed the
problem.

Well, I don't believe this, but I pulled out an ole' crufty looking
double density wire IDE cable from my closet swapped out the one
that came with my motherboard (Gigabyte) and rebooted, and now
suddenly dfly does UDMA100. What I don't understand is why both
the Linux Kernel and Windows XP ran the HD with the other cable at
UDMA100 without any problem.

Fwiw, I once had a system setup with multiple-OS's, and had a
similar problem where FreeBSD wouldn't recognize a drive as ATA/100
while some other OS's seemed to be happy (*). Years went by without
me figuring it out. Finally it was time to ugprade, and while moving
hard-disks to a new machine I noticed that the IDE cable had been put
in backwards. The end that was supposed to plug into the drive was
plugged into the motherboard, and (obviously) visa-versa. I switched
the cable around so that it was connected correctly, booted up, and
FreeBSD was happy with it. So then I shutdown the PC again and moved
the hard drive to the new PC. I managed to figure it out on the
very day that "it just didn't matter anymore"...

(* - I know that the other OS's *reported* an ATA/100 connection, but
I never checked to if they were really using the drive at that speed.
Also, this was long enough ago that it might have been ATA/66 and not
ATA/100, but the basic idea is the same).